What Causes You To Have Brain Metastases?

Brain metastases will usually occur when the cancer cells travel through the bloodstream or the lymph system from the original site to the brain. The tumor cells will start to grow there rapidly crowding and destroying nearby tissue. Sometimes a patient might have multiple metastatic tumors in several different areas of the brain. Some metastatic brain tumors appear many years after the primary cancer while in other cases they metastasize so quickly that they are identified before the primary tumor. ¹Sometimes the body’s defense system is also able to destroy the primary tumor but it cannot control the metastasis to the brain and in this case the primary cancer remains unknown.²

The symptoms of brain metastases vary depending on the tumor’s size, number, location and its rate of growth. They include headache that can be with nausea and vomiting, mental changes such as increasing memory problems, seizures, dizziness, weakness in the arms and legs, loss of balance, behavior and personality changes, speech disturbances, blurred vision/vision disturbances, numbness and hearing loss.³ The risk of developing brain metastasis increases after the age of 45 years and is highest in those over 65 years of age.⁴

It is important to see a doctor if you have persistent signs and symptoms that are interfering with your daily activities. It is also important to tell your doctor if you have been treated for cancer in the past. The most common causes of brain metastases include patients of lung cancer (48%), breast cancer (15%), genitourinary tract cancers (11%), osteosarcoma (10%), melanoma (9%), head and neck cancer (6%), neuroblastoma (5%), gastrointestinal cancers especially colorectal and pancreatic carcinomas (3%), lymphoma (1%).⁵ Out of these tumors lung cancer and melanoma are most likely to present with multiple metastasis while others mostly present with a single metastasis.

Brain imaging such as CT scan and MRI is needed to determine the presence of brain tumors. Biopsy will be performed to confirm the diagnosis. The treatment options depend on the condition of the patient and presence of primary tumor its response to treatment along with its current status. Surgery provides instant relief as it releases pressure inside the skull that results due to increasing size of tumor and swelling of the brain.⁶ The brain metastases patient might find relief within hours of surgery if the symptoms were caused due to mass effect on the brain. But a surgery is only performed if the primary tumor is treatable and under control and there is a single metastatic tumor. The treatment is usually palliative and the goal of therapy is to reduce symptoms of metastasis and prolong the life of the brain metastases patient. In healthier younger patients aggressive therapy can be done if required that involves craniotomy with maximal excision, chemotherapy and radiosurgical intervention.

Symptomatic care includes corticosteroid therapy to prevent the development of cerebral edema and treat other neurological symptoms such as headaches, cognitive dysfunction and emesis.⁷ The prognosis of the metastasis depends upon the type of primary cancer present, age of the brain metastases patient, the absence and presence of extracranial metastases and number of metastatic sites on the brain. People who do not undergo treatment the survival rate is approximately one to two months. While in younger brain metastases patient with a single mass in brain the prognosis is much better.⁸

Brain metastases occur when the cancer cells have spread from primary tumors in other organs of the body to the brain. They are also known as secondary tumors. The metastatic tumors are among the most common mass lesions in the brain. About one third of the patients having tumors anywhere in the body will have brain metastases. The cancerous cells break off from a tumor and travel through the bloodstream or the blood lymph system and reach the brain. The most common types of tumors that metastasize to the brain are lung cancers, melanomas, breast carcinomas, and colon and kidney cancers.

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